Rotary pump



gNo Model.)

1?. M. ROOTS.

ROTARY PUMP.

No. 325,276. Patented Sept. 1, 1885.

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FRANCIS M. ROOTS, OF CONNERSVILLE, INDIANA.

ROTARY PUMP.

SPECIFICATION forming part of Letters Patent NO. 325,276, datedSeptember 1, 1885.

(X0 model.)

To aZZ whom it may concern.-

Be it known that I, FRANCIS M. Roo'rs, a citizen of the United States,and a resident of Oonnersville, in the county of Fayette and State ofIndiana, have invented certain new and useful Improvements in RotaryPumps, of which the following is a specification.

The object of the invention is an improved rotary abutment that can beconstructed with less labor and with greater accuracy than those now inuse, and that will occupy less of the air-space within the shell, andthus increase the capacity of the machine.

Vith these objects in view my invention consists in a piston theopposite major and minor convex curves of which are composed of arcs ofcircles of different radii, cut from common centers, whereby the laborof handling the abutments in finishing them for use is reduced one-half,and accuracy in dressing to the proper shape attained.

In my Patent No. 264,962, dated September 26, 1882, the compound convexcurves or contact-surfaces were all described from different centers,and the abutments, when mounted between templets for dressing, were madeto turn around these centers as axes, as described in my Patent No.247,691, dated September 27, 1881. This required a great deal ofhandling, and as it is difficult to have so many holes on the templets(eight in each one) and get each hole perfectly concentric with thepoints from which the major and minor curves of the pistons aredescribed, the slightest inaccuracy in centering the piston in thedressing-tool would of course affect the accuracy of the abutment, andperfect contact of the pistons during their entire revolution in thepump was not always attained, especially in the larger machines.

By my present invention I have overcome all these difficulties, and amable to produce a perfect machine having much greater capacity by reasonof the diminished ends of the abutments, and greater strength by reasonof the shortened waist between the pistons. I will here remark that whenI speak of abutment I mean the two pistons, one at each end, with thewaist formed by the two recesses which connects the two pistons; andwhen I speak of pistons I mean the convex parts of the abutments whichkeep up contact with each other and the case when the pistons arerevolving.

In order to distinctly point out the difference between my presentinvention and that shown in my previous patent, No. 264,962, upon whichthis invention is an improvement, I have shown in the drawings at Figure2 a diagram illustrating the form of pistons of my said former patentand the method by which they were produced; and Fig. 1 is a diagramillustrating my newly-invented piston and my new method or system forobtaining the points from which, as centers, the compound curves formingthe contact-surfaces of the pistons are described.

I will first describe my present invention, and then by reference toFig. 2 point out how it is distinguished from my former inventions.

Referring now to Fig. 1, the shafts A A upon which the abutments aremounted are placed the proper distance apart, depending upon the size ofthe machine to be constructed. Two equal circles, P, are describedaround the shaft-centers by a radius equal to half the dis tance betweensaid centers. These are the pitch circles. \Vithin the pitch circles Pand from the same centers I describe two smaller circles, I, by a radiusequal to three-fourths of the radius of the pitch circles. This I termthe inscribed circle. Both of these circles are divided into four equalparts by the radial lines X Y. Vithin the pitch circle I inscribe asquare by the lines O,which intersect the pitch circle at the samepoints where the lines X and Y cut the same. \Vhere the lines 0 cut theinscribed circle upon each side of the lines X and Y at j, are thecenters from which the compound curves of the pistons are described. Inow divide the inscribed square into four equal parts by the radiallines Z, and through the centers j, I draw the lines L, extending thembeyond the pitch circle for the purpose of obtaining the radius by whichthe minor curves of the pistons are described.

To obtain the radius of the major curve I place one foot of the dividersin one of the pointsj, and extend the other across the line X or Y tothe point a,where the diagonal line Z cuts the pitch circle. Vith thisradius all the outer or major curves of the pistons are described. Themajor curve is continued through the pitch line P to the point 7:,whcreit meets the line L. Now,with one foot of the dividers in pointy, Iextend the other to the point It. This gives me the radius by which allthe minor curves are described from the centers j. These curves meet themajor curves at points 70, and extend a short distance within theinscribed circle and lines 0. The major curves extend from points it ashort distance across the lines 0, at the outer ends of the pistons.

The ends of the pistons, instead of being left sharp at the apex or endsof the pistons, as is shown by dotted lines, may be turned off, as shownby the curved linesp 12, so as to give more bearing-surface against thecylindrical part of the case; or grooves may be planed in I the ends ofthe pistons, as shown, to be fitted with adjustable or spring packing,as most desirable for the duty required; or the ends may be packed, asshown in Fig. 2. The spaces from the points in the major curve, (marked9a,) to where the ends of the pistons come in contact with the case, notbeing necessary to keep up contact, are cut back, as shown at 0. Theseneed not be dressed, and are left in the rough.

The recesses of the abut-ments are described from the points ten theminor axes of the abutments, so as to give the piston ends ainpleclearance. The recesses have no part to perform in keeping up contactbetween the pistons. They therefore require no dressing, but may be leftin the rough, as their only of fice is to clear the ends of the pistonsto permit them to revolve.

The construction of the case, its supports, the driving mechanism, andbearings are the same as described in my former patents above referredto, are well known to those skilled in the art, and therefore need notbe illustrated or described herein.

The circles surrounding the points j j, Fig. 1, and 2" and 4, Fig. 2,represent the holes bored in the templets (the templets are the exactsize and shape of the ends of the abutments) to receive the centerswhich support the abutments in the dressing-tool while the pistons arebeing finished.

It is evident from an examination of the two diagrams, Figs. 1 and 2,that the number of centers is reduced from eight in the latter to fourin the former: consequently the labor of centering and handling isreduced one-half,

as when the abutment, Fig. 1, islnounted up on one of the centers themajor curve is first dressed, and then the abutment turned halfwayaround and the minor curve upon the opposite side dressed. Thisoperation is re peated until all the contact-surfaces are dressed downto the templets.

I have drawn in dotted line at Fig. 2 the form of my improved piston toclearly show the difference in working capacity between the new and theold form of piston. The metal of the pistons outside of the dotted linesbeing removed in the new pistons leaves, of course, just so muchadditional air-space within the shell or case. As this increased volumeof air is taken in and forced out at each revolution of the abutments,itwill be readily understood that the capacity ofthe machine is greatly increased.

It is evident that a good and effective pump may be made by slightlyvarying the centers from the pointj; but these centers are, it isbelieved, in the exact position to giv the best results.

Having thus fully described my invention, what I claim as new, anddesire to secure by Letters Patent, is

Pistons for rotary pumps, constructed substantially as hereinbefore setf0rththat is, having the convex abutting surfaces composed of arcs ofcircles at different radii, the centers from which said several arcs aredescribed being the pointsj, which are common centers to the major andminor curves on opposite sides of the major axis X Y.

FRANCIS M. ROOTS.

Witnesses:

Gno. J. lVIURRAY, ALFRED BENEDICT.

